Puffer piston circuit breakers are electrical power circuit breakers wherein the flow of quenching gas for extinguishing the electrical arc during a disconnecting action is produced simultaneously with the motion of the moving contact by a cylinder which is displaced toward a cooperating stationary piston, or vice versa, such that the space within the cylinder is reduced and the gas present therein is compressed. In the course of the continuing disconnecting motion the compressed gas is conducted to the point of contact disconnection, and thus to the electric arc, where it extinguishes the latter.
In puffer piston circuit breakers of the aforedescribed type, either the puffer piston or the puffer cylinder is driven, together with the moving contact, by an externa1 drive which is required to supply the power neccessary to accelerate the moving masses, to overcome frictional forces and to compress the quenching gas present in the puffer cylinder. These requirements demand a high power drive, which amounts to a significant part of the overall cost of the circuit breaker.
The power required of the external drive may be reduced, while maintaining the disconnecting capacity of the circuit breaker, by obtaining at least part of the energy needed to generate the extinguishing gas flow from the arc itself. One such puffer piston power circuit breaker is disclosed in German Patent No. DE-OS 23 49 263, wherein outside the compression space of the puffer cylinder an auxiliary arc is ignited, which increases the temperature and thus also the pressure, of the gas in the combustion space, and thereby accelerates the puffer piston with an additional driving force. It is also known, for example, from French Patent No. 858,497, to generate an additional flow of gas by means of an auxiliary arc which supplements the gas flow of the puffer piston.
Both of the aforementioned prior art solutions require an auxiliary arc, which has the disadvantage of making the use of specialized contacts necessary. In addition, such contacts are also subject to burning out after a period of time in a manner similar to the principal contacts. Hence, not only the main contacts, but also the separately located auxiliary contacts, must be periodically replaced.
A further undesirable side effect of the generation of the flow of quenching gas by means of an auxiliary arc is that the quenching gas is further heated, thus reducing its quenching capacity.